Antibiotics, which act by either killing or stopping microbial growth, have been used extensively in the control and prevention of infectious diseases. However, this live-or-die selection pressure has inevitably fostered the emergence of superbugs that are resistant to multidrugs. Infections associated with antibiotic-resistant pathogens are increasingly common in clinical and nosocomial settings (Pfaller et al., 1998; Livermore, 2004). Such infections have become a serious public health concern. In addition, it is known that bacterial pathogens can form biofilms, in which single-celled bacteria individually interconnect with each other through extracellular matrix. The biofilm bacterial cells could escape the human defense responses and withstand a high dose of antibiotics (Costerton et al., 1995).
When a pathogen encounters host organisms, whether it can establish infection or not is determined by the outcome of host-pathogen interactions. It is believed that any molecule that could fundamentally alter the balance between the host defense mechanisms and the pathogen virulence in favor of the host might be of practical value to prevent and control pathogenic infections (Zhang and Dong, 2004). Therefore, there remains a need to develop new treatments for the control and prevention of microbial infections.